William Ó Con Ceanainn

William Ó Con Ceanainn, Lord of Uí Díarmata, died in 1478.

Overview
Sub anno 1478, the Annals of the Four Masters state that

"Thomas O'Concannon, Lord of Hy-Diarmada, was slain by the son of his own brother."

He was succeeded by William, who died later the same year, who was in turn succeeded by his son, Davock.